Twisted pairs are a type of universal wirings formed by winding two mutually insulated conductors according to certain specifications, and belong to information communication network transmission medium. The twisted pairs are classified into STPs (Shielded Twisted Pair) and UTPs (Unshielded Twisted Pairs). The UTPs are widely used in Ethernet and telephone lines, and a type of UTPs formed by four pairs of transmission lines of different colors are usually used in Ethernet data transmission. In telephone trunk lines, a cable is generally formed by many (for example, 25, 100 or more) UTPs. Technologies for transmitting signals based on UTPs are numerous, where technologies such as ADSL (Asymmetric Digital Subscriber Line), HDSL (High bit Rate DSL) already have a wide application base. For the convenience of description, the technologies such as ADSL and HDSL are generally called xDSL technology.
In a conventional xDSL technology for transmitting signals based on UTPs, N UTPs are generally used as N channels to transmit signals. With the further development of high-speed services, the communications capacity of the xDSL technology and the access rate provided by the xDSL technology cannot meet the requirements of users. Accordingly, a method for extending channels is provided in the conventional art. In a series common mode, based on the N channels of the N UTPs, (N−1) channels are extended, and the number of the extended channels is up to 2N−1. According to the method, a new channel is extended between each two adjacent UTPs, the transmission manner of the original channel is not changed, and the DM (Differential Mode) of the channel is still used to transmit signals, while a signal transmitted over the extended channel is divided into two parts, which are transmitted separately by using the CM (Common Mode) of the corresponding two original channels, and common-mode signals over the two channels are differentiated at a receiving end to obtain a signal of the extended channel.
However, in the conventional art, a signal transmitted over the extended channel is divided into two parts, which are transmitted by using a UTP separately, so the transmission performance of the extended channel is not maximized.